It has been widely reported that Senator Tim Johnson of South Dakota was treated on Wednesday, Dec. 13, for a ruptured arteriovenous malformation, or AVM. To learn more about this condition, we contacted Michael Lawton, MD, associate professor of neurological surgery at UCSF and an expert on AVMs.
Q. What is an AVM?
A. AVMs, or arteriovenous malformations, are tangles of abnormal blood vessels in the brain. They consist of a blood vessel nidus (nest) in which arteries connect directly to veins, instead of through the elaborate collection of very small vessels called capillaries. It is thought that patients are born with AVMs, but as the years go by, they can enlarge as the pressure and blood flow through the arterial vessels wear down the vascular tissues. The danger of an AVM is rupture or hemorrhage, which can be due to aneurysms in the arteries that feed it or from the veins that drain out of it, which are ill-equipped to handle the heavy flow through them.
Q. How common are AVMs?
A. About 300,000 Americans are believed to have one in the brain or spinal cord - although only about 12 percent of them, roughly 36,000, will notice symptoms such as headaches or seizures. It's a condition people are born with, but symptoms rarely arise until patients are older. AVMs typically present with hemorrhage or rupture, but can also produce seizures or neurological deficits from the AVM shunting or stealing blood flow away from adjacent, normal brain tissue.
Q. Is this dangerous?
A. The greatest danger from these brain tangles is bleeding. A small leak from inside the nidus may never be detected, and may not cause lasting damage. But a larger hemorrhage could cause severe damage to the brain, with 10 percent of hemorrhages resulting in death and 25 percent resulting in neurological deficits.
Q. What can be done to stop it?
A. If an AVM has bled and/or is in an area that can be operated upon, then surgical removal may be recommended. The patient is put to sleep with anesthesia, a window through the skull is opened and the AVM is surgically removed. When the AVM is completely removed, it is considered cured.
Q. How do you think Senator Johnson will be?
A. There really is no way to tell without reviewing his condition after the bleeding, the anatomy of his AVM and his condition after surgery. As the details of his case are made public, his prognosis will become clear. Most patients with AVMs that are treated surgically have an excellent chance of recovery and a high rate of cure.
Related Links:
Lawton Laboratory
UCSF Center for Cerebrovascular Research
UCSF Targets Cerebrovascular Malformations
Neuroscience at UCSF Medical Center, Fall 2005
